The public switched telephone network (PSTN), with its impressive coverage, reliability and ease of use, is the reference standard in voice communications and related services. Users have grown to expect a dial tone every time a phone is taken off-hook, and to be connected to a dialed party in a quick and efficient manner over a high quality connection. Users are not only accustomed to, but demand, residential and business services, such as caller identification, call forwarding, and call waiting. The PSTN and its related services are being further extended at a rapid rate by wireless networks.
Although the circuit-switched networks of the PSTN and wireless networks dominate voice communications, there is an increasing market to provide voice and related services over packet-switched networks, such as the Internet. These voice and related services provided over packet-switched networks are typically referred to as IP telephony. Given the extended coverage of the PSTN and wireless networks, there is a need to have these networks interact with packet-switched networks to provide seamless communications between users on the respective networks.
The PSTN can provide business and customer groups across multiple agent types within the PSTN infrastructure. For example, a customer group may include all subscribers in one building on a large company's campus. Traditionally, all of the members within the customer group are supported using a common telephony infrastructure. Although these customer groups may be connected to packet-switched networks through existing gateways, subscribers on the different networks cannot coexist in a common business group. Within a given business group, it is often preferable to define and support multiple appearance directory number (MADN) groups, wherein multiple terminals share a common directory number.
MADN terminals are generally supported by a common switch. For incoming calls directed to the MADN group using the common directory number, the terminals are controlled to ring at the same time, any terminal within the MADN group can answer the call. The first terminal to answer receives the call; however, other members within the MADN group may subsequently join the call. Unfortunately, MADN groups are only supported in the PSTN. As such, MADN groups may not include packet-switched terminals supporting IP telephony. Further, the inability to support packet-switched terminals eliminates the opportunity to support mobility within a MADN group without reconfiguring infrastructure.
Unfortunately, IP telephony has been plagued with unreliable connections, poor quality of service, and limited services as compared to the PSTN. Call signaling and related provisioning are typically provided separately within the various networks, resulting in inefficient operation and limited or incompatible services between the networks. As such, there is a need for a way to support MADN groups including packet- and circuit-switched terminals within the same group.
There is also a need for a way to support IP telephony by the PSTN wherein telephony terminals on the PSTN or packet-switched network appear the same to users and can access and support a complete set of business or residential services normally supported by the PSTN. Further, there is a need to provide these services to IP terminals in an efficient manner while minimizing the impact on the PSTN entities providing for voice communications and related services.